Digestion Absorption (Lec 6)

Question 1

Final breakdown and absorption occurs?

Answer 1

SI

Question 2

Only what Carbs can be digested?

Answer 2

monosaccharides

Question 3

Polysacch (starch, glycogen) Δd to?

Answer 3

Disaccharide by saliva and pancreatic amylase

Question 4

Disacch (maltose, sucrose, lactose) Δd to?

Answer 4

monosacch by enzymes in brush border of SI

Question 5

Glucose and Galactose absorbed from GI tract into epithelium how?

Answer 5

Na+-dependent transport (thru SGLT1 symport)

Question 6

Fructose absorbed absorbed from GI tract into epithelium how?

Answer 6

facilitated diff (GLUT-5 symport)

Question 7

Glu, Galac, Fru exit basomembrane of epithelial cell how?

Answer 7

facilitated diff (GLUT-2)

Question 8

Glu, Galac, Fru enter blood how?

Answer 8

simple diffusion

Question 9

Maltose Δd to?

Answer 9

2 glucose

Question 10

Lactose Δd to?

Answer 10

glu and galac

Question 11

Sucrose Δd to?

Answer 11

glu and fru

Question 12

Protein digested by what?

Answer 12

Pepsin from chief cells in stomach

Pancreatic enz from acinar cells in brush border of SI

Question 13

Pancreatic enz in SI can’t digest proteins until?

Answer 13

They’re activated by membrane-bound enteropeptidases:

Trypsin
Chymotrypsin
Carboxypeptidase

Question 14

Amino Acid absorbed from GI tract into epithelial cells how?

Answer 14

Na+-dependent transport (cotransporter)

Question 15

Amino Acid exit basomembrane of epithelial cells how?

Answer 15

facilitated diff

Question 16

AA enter blood how?

Answer 16

simple diff

Question 17

What enz hydrolyzes peptides into free AA in epithelial cells?

Answer 17

cytosolic peptidase

Question 18

Triglycerides digested/absorbed how? (7)

Answer 18

1) emulsification by bile
2) pancreatic lipase hydrolyzes into monogly and FA
3) formed into micelle -> to SI epith surface
4) Monogly and FA released
5) resynth into trigly, coated w/ lipoprotein = chylomicrons
6) exocytosed thru basomem
7) enter lymph vessels

Question 19

Ca2+ absorption in SI requires?

Answer 19

vit D3

Question 20

Steps of Ca2+ absorption in SI? (3)

Answer 20

1) facilitated diff into apical memb
2) vit D3 stim Ca2+BindingProtein
3) Ca2+ATPase and Na+/Ca2+ exchange release it from basomemb

Question 21

Fat-solu vitamins?

Adsorbed how?

Answer 21

A, D, E, K

same as lipids (in micelles)

Question 22

H2O-solu vitamins?

Absorbed how?

Answer 22

Bs, C, biotin, folate

Na+-dependent transport

except B12 binds to IF so not absorbed until ileum

Question 23

Iron absorption, 2 kinds?

Answer 23

Heme and Fe2+

Question 24

Heme Iron absorption?

Answer 24

If immediately needed for RBC, use membrane ion transporter ->
bound to transferrin to move thru blood to bone marrow

Question 25

Fe2+ Iron absorption?

Answer 25

If no immediate need, stored in epi cells as ferritin

can NOT be used later for RBC